Medical device heaters and methods

ABSTRACT

A medical device having a heater with at least one heating element which has mains voltage applied to it by a heating control unit. The heating control unit includes a monitoring arrangement and a switching arrangement. The monitoring arrangement can recognize the zero crossings of the mains voltage, and the switching arrangement can switch the at least one heating element on or off in the zero crossing. The heating control unit controls the power of the heating by switching on and off of one or more half cycles of the mains AC voltage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/315,240, filed Dec. 8, 2011, which claims the benefit under 35 U.S.C.§119(e) of U.S. Provisional Patent Application No. 61/421,332, filed onDec 9, 2010, which is incorporated by reference, and claims priorityunder 35 U.S.C. §119(a) to German Patent Application No. 10 2010 053973.2, filed on Dec. 9, 2010.

TECHNICAL FIELD

The present invention relates to medical device heaters and methods.

BACKGROUND

In dialysis machines, heating of dialysis fluid is usually realized asan ohmic heating element to which a heating control applies mainsvoltage to switch the heating element on or to disconnect the heatingelement from the mains voltage in order to switch it off.

The heating power can be set and adapted to the different rated voltagesto split the heater into a plurality of heating elements or to controlthe heating elements via a phase angle control. Phase angle controlsare, however, complicated and moreover have problems withelectromagnetic irradiation. There is moreover a substantial power lossin the electronic system. The previously known division into a pluralityof heating elements furthermore has the disadvantage that the deviceshave to be switched differently at different rated voltages of the mainspower in order not to reach any unpermittedly high power consumption.

SUMMARY

In one aspect of the invention, a medical device (e.g. a dialysismachine) has a heater with at least one heating element as well as aheating control unit. The heating control unit applies mains voltage tothe heating element. The heating control unit in this respect includes amonitoring arrangement and a switching arrangement. The monitoringarrangement can recognize the zero crossings of the mains voltage, andthe switching arrangement can switch the at least one heating element onor off in the zero crossing.

The heating control unit controls the power of the heating via theswitching on and off of one or more half cycles of the mains voltage.

Individual half cycles of the mains voltage can be switched on or off inthis process. However, pulse packets can naturally also be connectedwith a plurality of half cycles or periods of the mains voltage. In thisrespect, the power is set via the ratio of the number of the half cycleswith a switched on heating element to the number of the half cycles witha switched off heating element. In this respect, the irradiation, thenumber of components, and the power loss in the electronic system isconsiderably reduced with respect to a phase angle control.

In an advantageous embodiment of the present invention, the monitoringarrangement detects the level of the mains voltage, and the heatingcontrol unit adapts the control of the at least one heating element tothe detected level of the mains power supply. The medical device (e.g.dialysis machine) can be operated at different rated voltages of themains voltage. The control of the power of the heating via the switchingon and off of one or more half cycles of the mains voltage in particularallows an operation at different rated voltages of the mains powersupply and/or allows an adaptation to fluctuating voltage levels of themains power supply. The same maximum power of the heating at differentmains AC voltages can in particular thus be provided. In this respect,the ratio of the number of the half cycles with a switched on heatingelement to the number of the half cycles with a switched off heatingelement is adapted to the detected level of the mains power supply, sothat in each case the same maximum power of the heating is availableindependently of the level of the mains power supply.

The medical device (e.g. dialysis machine) can furthermore have at leasttwo heating elements which can be switched on and off independently ofone another by the switching arrangement. The division into two heatingelements in this respect permits an even more flexible control of thepower of the heating.

In this respect, with regard to the above-described control of the powerof the heating via the number of the half cycles with a switched onheating element or with a switched off heating element, the number ofthe half cycles at which the first heating element is switched on andthe number of half cycles at which the second heating element isswitched on are advantageously added together, optionally while takingaccount of a factor for considering different rated powers of the twoheating elements. The same applies to the number of the half cycles witha respective switched off first or second heating element.

In this respect, the heating control unit advantageously has a firstoperating mode in which the two heating elements are operated partiallyor fully synchronously. The two heating elements in this respect inparticular have rated voltage half cycles applied synchronously in partor in full. A correspondingly higher power can also be achieved with alow supply voltage due to the synchronous operation of the two heatingelements. In this respect, both heating elements can be switched offsynchronously for a corresponding number of half cycles. Alternatively,however, it is also conceivable only to switch off one of the twoheating elements in each case to reduce the power.

In some embodiments, the heating control unit has a second operatingmode in which the at least two heating elements can be operatedalternately. The two heating elements in this respect have a specificnumber of mains voltage half cycles applied alternately. In this secondoperating mode, for all mains voltage half-cycles in which the firstheating element is switched on, the second heating element is switchedoff and vice versa. With this alternating operation, both heatingelements can naturally also be switched off. The alternating operationof the two heating elements, in particular the operation of the twoheating elements with one respective half cycle, makes it possible tomaintain the amperage and/or power in a permitted range even at highsupply voltages. The two heating elements are in this respect operatedalternately with sequential half cycles.

In some embodiments the heating control unit selects the first or secondoperating mode in dependence on the detected level of the mains powersupply. It can thus be ensured that the same maximum heating power isprovided despite different rated voltages of the mains power supply.Currents which would overload the mains power supply and/or the heatingelements can furthermore be avoided by the second operating mode, evenat high rated voltages.

The heating control unit advantageously selects the first operating modeon detection of a mains AC voltage which is in a first, lower voltagerange and the second operating mode on detection of a mains AC voltagein a second, higher voltage range. The first, lower region in thisrespect advantageously includes at least one mains AC voltage between100 V and 120 V, (e.g., 100 V, 110 V or 120 V). The second higher rangeadvantageously includes at least one mains AC voltage between 230 V and250 V (e.g., 230 V or 240 V). In some embodiments, the first rangeincludes the range between 90 V and 110 V. The first range canalternatively include the range between 80 V and 130 V or between 80 Vand 160 V. The second range can advantageously include the range between220 V and 240 V. The second range can alternatively include the rangebetween 180 V and 250 V or between 160 V and 250 V.

In an operation in the first and/or second operating modes, the ratio ofthe number of the half cycles with a switched on heating element to thenumber of the half cycles with a switched off heating element isadvantageously set in dependence on the level of the detected mains ACvoltage. With a mains AC voltage which lies within the respectivevoltage range in which an operation takes place in the first and/orsecond operating modes, the maximum power of the heating can be keptconstant and/or a desired power can be set.

The medical device can in this respect be operated in the firstoperating mode so that the two heating elements for setting the powerare not acted on by all mains voltage half cycles, but are ratherswitched on and off synchronously or alternately for one or more mainsvoltage half cycles.

In the second operating mode, not every half cycle is switched either tothe one or to the other heating element, but a corresponding number ofhalf cycles is not switched to any of the heating elements to reduce thepower. The number of mains voltage half cycles which can act on theheating elements can be changed accordingly depending on the level ofthe mains AC voltage.

The above described devices and methods can also be used with more thantwo heating elements. For the example, the above described devices andmethods could be implemented with three or four heating elements, wherethe three or four heating elements each alternately have half cyclesapplied in the second operating mode, so that a half cycle is always asa maximum switched to one of the heating elements. The alternateoperation can in this respect take place, for example, in that one ormore half cycles are sequentially switched to the individual heatingelements. The heating resistance of each individual heating element canhereby be increased and thus the maximum power consumptioncorrespondingly reduced at a high mains voltage. At a low voltage, theheating elements can then be operated in parallel in the first operatingmode. More than four heating elements are naturally also conceivable inthis respect.

In the above-described embodiments, the power of the heating was adaptedto different levels of the mains power supply via the switching on andoff of one or more half cycles of the mains voltage. The maximum powerof the heating can thus be kept the same for different mains voltages.In addition, the occurrence of unpermittedly high currents can beavoided.

The devices and methods described herein can, however, also be used toset the power of the heating to a value below the maximum power forpurposes of temperature regulation. The present invention can, forexample, be used to set the heating to a value between 0 and 10% of themaximum power. The currently output power can also here be set by theratio of the number of the half cycles with a switched on heatingelement to the number of the half cycles with a switched off heatingelement.

The medical device in this respect advantageously includes a temperaturesensor, wherein the ratio of the number of the half cycles with aswitched on heating element to the number of the half cycles with aswitched off heating element can be set in dependence on a signal of thetemperature sensor.

Such a temperature regulation can in this respect also be usedindependently of the adaptation of the power of the heating to differentmains voltages, in particular also with those devices which can only beused with a single mains voltage. Such a temperature regulation is,however, advantageously combined with an adaptation to the operatingvoltage of the mains power supply.

In some embodiments, the heating control unit generates a control signalon the basis of the signal of the temperature sensor which issuperimposed on the control signals for adapting the power to thedetected level of the mains power supply. Different embodiments areconceivable for such a superimposition.

In some embodiments, an envelope signal with a longer switching periodin comparison with the mains voltage period can be generated using thesignal of the temperature sensor. The envelope signal can besuperimposed on the adaptation of the power to the detected level of themains power supply working at one or more mains voltage half cycles.Alternatively, the ratio of the number of the half cycles with aswitched on heating element to the number of the half cycles with aswitched off heating element can be set directly smoothly in time independence on the signal of the temperature sensor and of the detectedlevel of the mains power supply.

In certain embodiments, one or more half cycles of the mains voltage areswitched on and off. For example, individual mains voltage half cyclescan be switched on and off. However, pulse packets of a plurality ofhalf cycles of the mains voltage can also be switched on and off. Forexample, pulse packets of 1 to 100 mains voltage half cycles (e.g., 1 to10 mains voltage half cycles) can be used.

The heating element is in this respect relatively slow in its reactionso that the temperature of the heating element does not rise and fall ina relevant manner with the switching on and off of the half cycles onthe use of a plurality of half cycles of the mains voltage, but ratheris only determined via the mean ratio of the number of the half cyclesswitched on and off. To achieve a setting of the power which is asfine-grained as possible over a large power range and/or a large rangeof mains DC voltages, the smallest number of switchable half cycles usedfor the control are typically, kept relatively low (e.g., at 1 to 5 halfcycles, at 1 to 3 half cycles).

The ratio of the number of the half cycles with a switched on heatingelement to the number of the half cycles with a switched off heatingelement is in this respect advantageously determined for a specific timeperiod or a specific number of half cycles and is used for the control.A typical time period in this respect can lie, for example, between 0.1and 20 seconds (e.g., between 0.5 and 5 seconds).

The heating control unit can switch the respective next half cycles onor off at any time so that the ratio remains at a desired value withinthe time period used for the determination.

It is equally conceivable to redetermine the ratio required for theprovision of the desired power of the number of the half cycles with aswitched on heating element to the number of the half cycles with aswitched off heating element after a fixed time period or after a fixednumber of half cycles and then to carry out a corresponding control inthe following time period or in the following fixed number of the halfcycles. A typical time period can in this respect lie between 0.1 and 20seconds (e.g., between 0.5 and 5 seconds). In this respect, the ratio isrecalculated on the basis of the measured mains AC voltage and of thedesired power.

The devices and methods described herein can be used in a dialysismachine wherein the heater is used for heating a medical liquid, such asdialysate or blood. In some embodiments, the medical device is aperitoneal dialyzer having a heater for heating dialysate. The devicesand methods described can equally be used in infusion devices, inparticular for heating an infusion solution.

The devices and methods can be used with any desired embodiments ofdialysis machine heaters, including throughflow heaters, heating bagheaters, and heaters for heating a presentation or supply bag.

A temperature sensor which directly measures the temperature of theheating element can be used as a temperature sensor for regulating thetemperature. Alternatively or additionally, a temperature sensor canalso be used to determine the temperature of the medium to be heated,such as the temperature of the dialysate used in a peritoneal dialysisdevice.

In addition to the medical device with a heater, certain embodimentsinclude a heating control unit for a medical device such as wasdescribed above. Such a heating control unit in this respect has theadvantages such as were already described above.

In another aspect, a method for operating a medical device having aheater with at least one heating element or for operating a heatingcontrol unit for such a device includes detecting the zero crossings ofthe mains voltage and switching the at least one heating element on andoff in the zero crossing, wherein the power of the heating is controlledvia the number of the half cycles of the mains voltage with a switchedon heating element.

The method advantageously takes place in this respect as was representedin more detail above with respect to the medical device. In thisrespect, the method can be a method for operating a medical device or aheating control unit of the type described above.

The heating control units described herein can improve the heatingmethods of medical devices by providing simple and effective heating forsuch medical devices.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other aspects,features, and advantages will be apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1a-1c illustrate three diagrams which show typical developments ofan automatic peritoneal dialysis treatment.

FIG. 2 is a schematic diagram of a peritoneal dialysis system.

FIG. 3 is a schematic diagram of the division of the peritoneal dialysissystem into a dialysis machine and a fluid system.

FIGS. 4a and 4b are perspective and plan views of a first embodiment ofa cassette.

FIG. 5 is a plan view of a second embodiment of a cassette.

FIG. 6 is a perspective view of a first embodiment of a dialysismachine.

FIG. 7 is a schematic fluid flowchart of a first embodiment of aperitoneal dialysis system.

FIG. 8 is a perspective view of a second embodiment of a dialysismachine.

FIG. 9 is a schematic fluid flowchart of a second embodiment of aperitoneal dialysis system.

FIG. 10 illustrates the coupling of the cassette in the secondembodiment of a peritoneal dialysis system.

FIG. 11 illustrates a first embodiment of a pump actuator.

FIGS. 12a and 12b illustrate the coupling of a pumping region of thecassette to a pump actuator.

FIG. 13 is a schematic diagram of the design of an embodiment of acontroller.

FIG. 14 illustrates a first embodiment of a heater that includes twoheating elements.

FIGS. 15a and 15b are diagrams which show the mains voltage half cyclesapplied to the two heating elements of the heater shown in FIG. 14 intwo different operating modes.

DETAILED DESCRIPTION

The function of a dialysis machine in which the heating devices andmethods described herein can be used will first be described generally.The dialysis machine to be described is a peritoneal dialysis machine.The components described below can, however, also be used in the samemanner or in a similar manner for a hemodialysis machine.

Peritoneal dialysis is a variant of artificial hemodialysis in which theperitoneum of the patient which has a good blood supply is used as afilter membrane natural to the body. Dialysate is introduced into theabdominal cavity via a catheter for this purpose. In accordance with theprinciple of osmosis, urea components of the blood diffuse through theperitoneum into the dialysate present in the abdominal cavity. After adwell time, the dialysate with the urea components is drained from theabdominal cavity.

In automatic peritoneal dialysis, a dialysis machine controls andmonitors the introduction of the fresh dialysate into the abdominalcavity and the draining of the consumed dialysate (also referred to asspent dialysate). Such a dialysis machine, also called a cycler, usuallyfills and drains the abdominal cavity several times overnight, while thepatient is asleep.

FIGS. 1a to 1c show three different procedures that are carried out by adialysis machine. One or more of these procedures is usually stored inthe controller of the dialysis machine. It is usually possible in thisrespect to adapt the stored procedures to the patient.

In FIGS. 1a to 1c , the dialysate quantity V respectively present in thepatient's abdominal cavity is shown over the time t. In this respect,FIG. 1a shows the development of a normal automatic peritoneal dialysistreatment overnight. At the start of the treatment, an initial outflowor drain 5 occurs during which dialysate which was left in the abdominalcavity of the patient during the day is removed. A plurality oftreatment cycles 1 then takes place. In FIG. 1a , three sequentialtreatment cycles 1 take place. Each treatment cycle comprises an inflowor fill phase 2, a dwell phase 3 and an outflow or drain phase 4. Inthis respect, a specific volume of fresh dialysate fluid is introducedinto the patient's abdominal cavity during the inflow phase 2. Themaximum permitted dialysate quantity in this respect amounts to betweenapproximately 1.5 and 3 L depending on the patient. The fresh dialysatenow remains in the abdominal cavity for a specific dwell time 3. Thedwell phase in this respect typically lasts some hours. The consumed orspent dialysate is then removed from the abdominal cavity again in theoutflow phase 4. A new treatment cycle then starts. The treatment isconcluded with a last inflow 6 by which a specific quantity of freshdialysate is introduced into the patient's abdominal cavity. It thenremains in the patient's abdominal cavity throughout the day.

The individual treatment cycles 1 which take place overnight are in thisrespect automatically controlled by the controller of the dialysismachine. The initial outflow and the last inflow can likewise becontrolled automatically by the dialysis machine. Alternatively, theycan be activated manually by an operator or by the patient.

A so-called tidal treatment is shown in FIG. 1b . This also starts withan initial outflow 5 and ends with a last inflow 6. A base cycle 7 isalso provided which is divided into a plurality of tidal cycles 8. Inthis respect, a base inflow phase 2′ is initially provided. After thedwell time 3, however, the complete dialysate volume is not drained fromthe abdominal cavity, but rather only a certain portion of the dialysatepresent in the abdominal cavity is drained. This is then replaced by acorresponding volume of fresh dialysate. After a further dwell cycle, afurther tidal removal can take place in which only a portion the totaldialysate present in the abdomen is removed. At the end of the basecycle 7, a base outflow phase 4′ takes place in which the totaldialysate is removed. Only one base cycle 1 is shown in FIG. 1b .Alternatively, however, a plurality of base cycles can also be provided.

The course of a peritoneal dialysis treatment with a so-calledperitoneal dialysis (“PD”) plus treatment is shown in FIG. 1c . In thisrespect, a conventional peritoneal dialysis treatment takes place duringthe night 9 and can, for example, e.g. be carried out in accordance withFIG. 1a or 1 b. An additional PD plus treatment is, however, alsoprovided during the day in which the consumed dialysate is removed in anoutflow phase 5′ and is replaced by fresh dialysate in an inflow phase6′. In the PD plus treatment, a normal night-time peritoneal dialysistreatment is combined with one or more additional treatment cyclesduring the day. The course of the night-time treatment is in thisrespect carried out as customary automatically by the dialysis machine.The treatment cycles during the day are likewise carried out andmonitored via the machine.

The design of a typical peritoneal dialysis system is shownschematically in FIG. 2. The peritoneal dialysis system in this respectincludes a container 10 with fresh dialysate and an outflow (e.g., adrain bag) 20 for used dialysate. A connector 30 is furthermore providedwhich can be connected to a catheter of the patient either to introducefresh dialysate into the abdominal cavity of the patient or to removeconsumed dialysate from the abdominal cavity. The container 10 withfresh dialysate, the drain bag 20 for used dialysate and the connector30 to the patient are in this respect connected to one another via fluidpaths 100 and form the fluid system of the peritoneal dialysis system.

A dialysis machine 40, also called a cycler, is provided for thecarrying out of the peritoneal dialysis treatment. The dialysis machine40 in this respect includes the following main components:

-   -   A pump 50 which is used for the transport of the fluids. The        pump 50 in this respect conveys the fresh dialysate from the        container 10 to the connector 30. The pump 50 can furthermore        transport the consumed dialysate from the connector 30 to the        drain bag 20.    -   Valves 70 which are used for the control of the fluid flows. The        valves 70 open and close the fluid paths 100 in order to        establish the corresponding fluid connections between the        container 10, the connector 30 and the drain bag 20.    -   A heater 60 which brings the fresh dialysate to a temperature of        approximately 37° C. before it is supplied to the patient. Since        relatively large quantities of dialysate are supplied directly        into the abdominal cavity of the patient in peritoneal dialysis,        the heater 60 is used to maintain the body temperature of the        patient within a desired range and to avoid an unpleasant        feeling caused by dialysate which is too cold.    -   Sensors 80 via which the proper procedure of the treatment can        be monitored and/or controlled. Temperature sensors can in        particular be used in this respect. Pressure sensors can        furthermore optionally be used.

The above-noted components of the dialysis machine 40 are controlled viaa controller 90. In this respect, the controller 90 controls the pump50, the heater 60 and the valves 70 on the basis of the data of thesensors 80. The controller 90 provides the automatic procedure of theperitoneal dialysis. The controller 90 includes a balance 95 whichbalances the fluid quantities supplied to and removed from the patient.The balance prevents the patient from being given too much fluid orhaving too much fluid removed.

The balance 95 can take place solely on the basis of the control dataand/or the sensor data for the pump 50. Alternatively, the balance canalso take place via separately provided balancing chambers. It isequally possible to use scales for the balancing. Such scales, forexample, weigh the weight of the container 10 with fresh dialysateand/or the container 20 with used dialysate.

Since the dialysate is dispensed to the patient directly into theabdominal cavity in peritoneal analysis, extreme sterility must beobserved. The fluid paths or the fluid system which come into contactwith the fresh dialysate and/or the used dialysate are therefore usuallydesigned as disposable parts. The fluid paths or the fluid system are inthis respect typically designed as plastic parts. They can thus besupplied in a sterile outer packaging and only unpacked briefly beforethe treatment.

In order to enable a control of the peritoneal dialysis by the dialysismachine 40, the fluid system can be coupled to the dialysis machine 40.In this respect, it is shown schematically in FIG. 3 how individualelements of the dialysis machine 40 are coupled to corresponding regionsof the fluid system.

The dialysis machine 40 in this respect has a heating element 61 to becoupled to a corresponding heating region 62 of the fluid system. Thecoupling in this respect enables the transfer of thermal energy from theheating element 61 to the dialysate present in the heating region 62.

The dialysis machine 40 also has one or more pump actuators 51 which areeach coupled to a corresponding pump region 52 of the fluid system. Thepump actuators 51 in this respect generate a pump force which istransferred to the pump region 52. The liquid present in the pump region52 can hereby be moved along the fluid paths.

The dialysis machine also has one or more valve actuators 71. Theygenerate a closing movement which is transferred to corresponding valveregions 72 of the fluid paths. The valve regions 72 of the fluid pathscan hereby be correspondingly closed or opened.

The dialysis machine also has one or more sensors 81. They are eachcoupled to a corresponding sensor region 82 of the fluid system. Thesensors 81 can hereby measure specific properties of the dialysate. Thetemperature of the dialysate can in particular be measured hereby.Provision can furthermore be made that the pressure in the fluid systemis determined.

The dialysis machine optionally has further actuators and/or sensorswhich are not coupled to the fluid paths.

The individual components of a peritoneal dialysis system are nowdescribed in more detail in the following with reference to embodiments.

1. Fluid System

1.1 Dialysis Container

Fresh dialysate is usually provided in plastic bags. Such plastic bagsusually have two layers of plastic film which are welded to one anotherin a marginal or peripheral region and thus form a container which isfilled with fresh dialysate. A hose element is usually welded to thiscontainer by which the dialysate can be removed from the bag. Aconnector is usually arranged at the hose element via which thedialysate container can be connected to the other fluid paths. The bagalso usually has a cutout or eyelet at the side disposed opposite thehose by which the bag can be hung onto a hook by it. It can hereby beensured that the dialysate flows out of the bag without problem.

The dialysate usually comprises a buffer, an osmotic agent andelectrolytes. Bicarbonate can, for example, be used as the buffer inthis respect. Glucose is usually used as the osmotic agent.Alternatively, glucose polymers or glucose polymer derivatives can alsobe used. The electrolytes usually include calcium and sodium.

The dialysate can be heat sterilized in this respect. Thisadvantageously takes place after the dialysate has been filled into thebag. Both the dialysate and the bag are hereby heat sterilized. In thisrespect, the filled bag is usually first packed into an outer packaging,whereupon the total system is sterilized.

Since the finished dialysate solution can often not be heat sterilizedor cannot be stored for a long time due to the ingredients, provisioncan be made to store individual components of the dialysate separatelyand only to combine them shortly before the treatment. A firstindividual solution in this respect usually includes the buffer, while asecond individual solution includes glucose and electrolytes.Optionally, more than two individual solutions, and thus more than tworegions, can also be provided in a bag. In this respect, a multi-chamberbag (e.g., a double-chamber bag), can be provided which has a pluralityof separate regions for the storage of the individual solutions. Theseregions are separated by a connection element which can be openedmechanically to mix the individual solutions with one another. Aso-called peel seam can, for example, be provided between the tworegions of the bag and opens on the application of a specific pressureto at least one of the regions of the bag.

Since relatively large quantities of dialysate are consumed during anight-time peritoneal dialysis treatment, a plurality of dialysatecontainers are usually used during the treatment. They are connected tothe fluid paths via corresponding connectors and can be used for thefilling of the patient by a corresponding connection of the valves.

1.2 Outflow

For the disposal of the consumed dialysis fluid, it can either be ledoff immediately into the drainage system or first be collected in anoutflow container. A bag (i.e., a drain bag) is usually likewise used asan outflow container in this respect. It is empty before the start ofthe treatment and can thus take up the consumed dialysate. The bag canthen be correspondingly disposed of after the end of the treatment.

1.3 Cassette

As already initially described, the fluid system has a plurality ofregions in which the dialysis machine has an effect on the fluid system.The fluid system is coupled to the dialysis machine for this purpose.

Cassettes are used to simplify the coupling of the fluid paths to thedialysis machine and the effect of the corresponding elements of thedialysis machine on the fluid paths. A plurality of regions in which thedialysis machine has an effect on the fluid paths are jointly arrangedin such a cassette. For this purpose, a cassette usually has a rigidbase of plastic into which chambers open to one side are introduced asfluid paths. These chambers are covered by a flexible plastic film whichprovides the coupling to the dialysis machine. The flexible plastic filmis in this respect usually welded to the rigid base in a marginal orperipheral region. The cassette is pressed with a coupling surface ofthe dialysis machine so that the actuators and/or sensors of thedialysis machine come into contact with corresponding regions of thecassette.

The cassette also has connections for the connection of the dialysatecontainer 10, the connector 30, of the drain bag 20.

A cassette in this respect usually includes at least one pump region andone or more valve regions. The liquid transport can thus be controlledby the fluid system via the cassette. The cassette can furthermore havesensor regions which enable a simple coupling of sensors of the dialysismachine to the fluid system. The cassette can optionally also have oneor more heating regions which can be coupled to corresponding heatingelements of the dialysis machine.

An embodiment of a cassette is shown in FIGS. 4a and 4b . It has a rigidbase 101 of plastic in which the fluid paths and coupling regions areintroduced as corresponding cutouts, chambers and passages. The rigidbase can in this respect be produced as an injection molded part or as adeep drawn part. The coupling plane of the rigid base 101 is covered bya flexible film 102 which is welded to the rigid base in a marginalregion.

During the treatment, the flexible film 102 is pressed with the rigidbase by the pressing of the cassette with a coupling surface of thedialysis machine. The fluid paths within the cassette are separated fromone another in a fluid tight manner by the pressing of the flexible filmwith the web regions of the rigid base.

The cassette has connections for the connection of the cassette to theother fluid paths. On the one hand, a connection 21 is provided for theconnection to the drain bag 20 as well as a connection 31 for theconnection to the connector 30. Corresponding hose elements (not shownin FIG. 4a ) can be provided at these connections. The cassette also hasa plurality of connections 11 for the connection of dialysate containers10. The connections 11 are designed as connectors to which correspondingconnector elements can be connected.

The connections are in each case in connection with fluid paths withinthe cassette. Valve regions are provided in these fluid paths. In thesevalve regions, the flexible film 102 can be pressed into the rigid base101 via valve actuators at the machine side such that the correspondingfluid path is blocked. The cassette in this respect first has acorresponding valve for each connection via which this connection can beopened or closed. The valve V10 is associated with the connection 21 forthe drain bag 20, and the valve V6 is associated with the connection 31for the patient connector 30. The valves V11 to V16 are associated withthe connections 11 for the dialysate container 10.

Pump chambers 53 and 53′ are provided in the cassette via whichcorresponding pump actuators of the dialysis machine can be actuated.The pump chambers 53 and 53′ are concave cut-outs in the rigid base 101which are covered by the flexible film 102. The film can be pressed intothe pump chambers 53 and 53′ or pulled out of these pump chambers againby pump actuators of the dialysis machine. A pump flow through thecassette can hereby be generated in cooperation with the valves V1 to V4which connect the accesses and outflows of the pump chambers 53 and 53′and are designated by the reference numeral 73 in FIG. 4a . The pumpchambers can in this respect be connected via corresponding valvecircuits to all connections of the cassette.

A heating region 62 is also integrated into the cassette. In thisregion, the cassette is brought into contact with or close proximity toheating elements of the dialysis machine which heat the dialysateflowing through this region of the cassette. The heating region 62 inthis respect has a passage for the dialysate which extends spirally overthe heating region 62. The passage is formed by webs 64 of the rigidbase which are covered by the flexible film 102.

The heating region 62 is provided at both sides of the cassette. Aflexible film is also arranged at the rigid base in the heating regionat the lower side 63 of the cassette for this purpose. The flexible filmis also welded to the rigid base in a marginal region. A passage islikewise arranged at the lower side and the dialysate flows through it.The passages on the lower side and on the upper side are formed by amiddle plate of the rigid base which separates the upper side from thelower side and on which webs are downwardly and upwardly provided whichform the passage walls. In this respect, the dialysate first flowsspirally on the upper side up to the aperture 65 through the middleplate from where the dialysate flows back to the lower side through thecorresponding passage. The heating surface which is available for theheating of the fluid can be correspondingly enlarged by the heatingregion provided at the upper side and at the lower side. Alternatively,the heating region can be arranged on only one side of the cassette.

The cassette also has sensor regions 83 and 84 by which temperaturesensors of the dialysis machine can be coupled to the cassette. Thetemperature sensors in this respect lie on the flexible film 102 and canthus measure the temperature of the liquid flowing through the passagedisposed below. Two temperature sensors 84 are arranged at the inlet ofthe heating region. A temperature sensor 83 via which the temperature ofthe dialysate pumped to the patient can be measured is provided at theoutlet at the patient side.

Another embodiment for a cassette is shown in FIG. 5. The cassette inthis respect substantially corresponds in its design to the cassette ofFIGS. 4a and 4b , but does not include any heating region. During use ofthis cassette, the heating therefore does not take place via a heatingregion integrated into the cassette, but rather via a heating bag whichis placed onto a heating plate of the dialysis machine or in some othermanner.

The cassette shown in FIG. 5 has fluid paths which can be opened andclosed via valve regions which are numbered consecutively from V1 toV16. The cassette also has connections for the connection to furthercomponents of the fluid system. In this respect, the connection 21 isprovided for the connection to the drain bag 20 and the connection 31 isprovided for connection to the connector 30 to the patient. Connections11 are also provided for the connection of dialysate containers 10.

Unlike the cassette of FIGS. 4a and 4b , the cassette shown in FIG. 5has a further connection 66 for the connection of a heating bag. In thisrespect, the liquid can be pumped into a heating bag via the connection66 for the heating of the fluid from the dialysate containers 10. Thisheating bag typically lies on a heating element so that the fluidpresent in the heating bag can be heated. The fluid is thereupon pumpedfrom the heating bag to the patient.

The pump chambers 53 and 53′ and the valves V1 to V4 correspond indesign and function to the corresponding components of the cassette ofFIGS. 4a and 4 b.

The cassette of FIG. 5 does not have any sensor region for theconnection of a temperature sensor. It is rather arranged in the regionof the heating elements. The cassette, however, has measurement regions85 and 86 for the measurement of the pressure in the pump chambers 53and 53′. The measurement regions 85 and 86 are in this respect chamberswhich are in fluid communication with the pump chambers and are likewisecovered by the flexible film. Pressure sensors at the apparatus sidewhich measure the pressure in the measurement chambers 85 and 86 andthus in the pump chambers 53 and 53′ can be coupled to the measurementregions.

The connection of the connections 11, 21, 31 and 66 of the cassette tothe further components of the fluid system takes place via hoseconnections. Connectors are optionally arranged at these hoseconnections.

1.3 Hoses

The connection between the individual containers of the system, thecassette and the patient connector usually takes place via hoseconnections. Since they are in each case disposable articles, the hosesare usually already fixedly connected at at least one side to a furtherelement. Hoses can, for example, already be provided at one or more ofthe connections of the cassette. Hoses can likewise already be in fixedcommunication with bags.

1.4 Connections

The fluid system is usually divided into a plurality of parts andpackaged in sterile form. These parts first have to be connected to oneanother for the treatment. The cassette and the dialysate bag or bagsare in this respect in particular packaged separately from one another.

The connections between the individual elements of the fluid systemusually takes place via connectors. The connectors are in this casedesigned so that they enable a sterile connection between the individualcomponents. This can occur, for example, via corresponding protectivefilms which are automatically opened on the closing of the connector.

The connection of the individual components can take place manually byan operator or by the patient him or herself. Provision canalternatively be made that the connection of the individual componentsis carried out automatically by the dialysis machine.

For this purpose, the corresponding connectors can be placed into aconnector receiver of the dialysis machine and can be automaticallyjoined together by the dialysis machine.

An electronic control can furthermore be provided which monitors thatthe correct components of the system are connected to one another.Identification means such as barcodes or RFIDs which identify thecomponents can be provided at the connectors for this purpose. Thedialysis machine in this respect includes an identification meansdetection unit such as a barcode reader or an RFID detection unit whichdetects the identification means on the connectors. The controller ofthe peritoneal dialysis can hereby recognize whether the correctconnectors were inserted.

Such a check of the correct assembly of the fluid system can be combinedwith an automatic connection of the connectors. The system thus firstchecks whether the correct connectors were placed into the connectorreceivers. The connection between the connectors is only established bythe dialysis machine when the correct connectors were inserted.Otherwise, the dialysis machine draws the attention of the user to thefact that the wrong connectors have been inserted.

2. The Dialysis Machine

The individual components of a dialysis machine will now be described inmore detail.

An embodiment of a dialysis machine is shown in FIG. 6 in which thecassette of FIGS. 4a and 4b is used. A schematic illustration of theperitoneal dialysis system resulting from this dialysis machine and thecassette of FIGS. 4a and 4b is shown in FIG. 7.

Another embodiment of a dialysis machine is shown in FIG. 8 in which thecassette of FIG. 5 is used. The dialysis system resulting from thecombination of this dialysis machine and the cassette of FIG. 5 isschematically illustrated in FIG. 9.

The two above-noted dialysis systems differ in the design of the heater,in the coupling between the dialysis machine and the cassette, and inthe design of the actuators and sensors.

2.1 Heater

The fresh dialysate has to be brought to body temperature before it isconveyed into the abdomen of the patient. The dialysis machine has acorresponding heater for this purpose.

The heating in this respect usually takes place via one or more heatingelements. The heating elements can, for example, be ceramic heatingelements. With such ceramic heating elements, a resistance strip isapplied to a ceramic carrier. The heating strip is heated by theapplication of a voltage to it, whereby the ceramic carrier material isalso heated. The ceramic heating element is in this respect usuallyarranged on a heating plate. It can be made of aluminum, for example.The fluid paths are in turn coupled to the heating plate so that thedialysate present in the fluid paths can be heated. Two differentdesigns are available for the heating of the fluid. On the one hand, alarger quantity of dialysate can first be heated which is only pumped tothe patient after the heating phase. This usually takes place via aheating bag which is placed on a heating plate of the dialyzer.

The heating bag can in this respect be the dialysis bag in which thedialysate is provided. Usually, however, a separate heating bag is usedin which the dialysate is pumped for heating. If the dialysate is heatedin the heating bag, it is pumped to the patient from there.

Such a concept is realized in the dialysis machine shown in FIGS. 8 and9. In this respect, a heating bag 67 is provided which lies on a heatingplate 68. The heating plate 68 is arranged on the upper side of theperitoneal dialysis machine so that it is easily accessible. The heatingbag 67 is connected to the cassette via a line 66′. The cassette has thevalves V5, V9 and V15 via which the heating bag 67 can be connected tothe other components of the fluid system. Fresh dialysate can thus bepumped from the dialysate containers 10 via the pump chambers to theheating bag 67. At the start of a treatment, the heating bag 67 is firstfilled with unheated dialysate. The dialysate in the heating bag 67 isthen heated to body temperature via the heating plate 68. The dialysateis then pumped to the patient via the pump chambers. The heating bag 67can thereupon be filled again so that the dialysate quantity requiredfor the next treatment cycle can be heated.

A temperature sensor 88, which is in contact with the heating bag 67 andcan thus measure the temperature of the dialysate in the heating bag 67,is advantageously provided in the region of the heating plate 68. Atemperature sensor can also be provided at the heating plate or at theheating element which measures the temperature of the heating element orof the heating plate. A corresponding controller makes sure that theheating plate does not become too hot for the material of the bag.

The heating bag 67 can additionally take over functions in the balancingof the fluid flows. The heating plate 68 can thus be part of scales 87via which the weight of the heating bag 67 can be determined. The fluidquantity which is supplied to the patient after heating can hereby bedetermined.

Alternatively to the heating of the dialysate via a heating bag, thedialysate can be heated while it is being pumped to the patient. Theheating thus works in the form of a continuous-flow water heater whichheats the dialysate moved through the fluid system while it is beingpumped through the fluid paths.

In this concept, a dialysate passage is provided which is coupled to aheating element of the dialysis machine. While the dialysate flowsthrough the dialysate passage, it takes up heat from the heating elementof the dialysis machine while so doing.

Such a concept is implemented in the dialysis machine which is shown inFIGS. 6 and 7. The heating region is integrated in the cassette in thisrespect, as was already shown above. On the coupling of the cassette tothe dialysis machine, the heating region of the cassette comes thermallyinto contact with heating elements of the dialysis machine.

The heating elements can in this respect likewise be designed as ceramicheating elements and can be in contact with heating plates which arecoupled to the heating region of the cassette. As already shown withrespect to the cassette, a respective heating plate which heats thedialysate flowing through the heating region is in contact both with theupper side and with the lower side of the heating region.

Respective temperature sensor regions are provided in the cassette atthe inflow and at the outflow of the heating region and come intocontact with temperature sensors of the peritoneal dialysate by thecoupling of the cassette. The temperature of the dialysate flowing intothe heating region and the temperature of the dialysate flowing out ofthe heating region can thus be determined by the temperature sensors T1to T3. Temperature sensors T4 and T5 are also provided to determine thetemperature of the heating elements and/or of the heating plates.

To enable a coupling of the actuators and/or sensors of the dialysismachine to the corresponding regions of the cassette, the dialysismachine has a cassette receiver with a coupling surface to which thecassette can be coupled. The corresponding actuators, sensors and/orheating elements of the dialysis machine are arranged at the couplingsurface. The cassette is pressed with this coupling surface such thatthe corresponding actuators, sensors and/or heating elements come intocontact with the corresponding regions in the cassette.

In this respect, a mat of a flexible material, such as a silicone mat,is advantageously provided at the coupling surface of the dialysismachine. It ensures that the flexible film of the cassette is pressedwith the web regions of the cassette and thus separates the fluid pathswithin the cassette.

A peripheral margin of the coupling surface is advantageously providedwhich is pressed with the marginal region of the cassette. The pressingin this respect advantageously takes place in an airtight manner so thatan underpressure or vacuum can be built up between the coupling surfaceand the cassette.

A vacuum system can optionally be provided to pump air out of the spacebetween the coupling surface and the cassette. A particularly goodcoupling of the actuators, sensors and/or heating elements of theperitoneal dialysis device with the corresponding regions of thecassette is hereby made possible. In addition, the vacuum system allowsa leak tightness check of the cassette. A corresponding vacuum isapplied after the coupling for this purpose and a check is made whetherthis vacuum is maintained.

The compression of the cassette against the coupling surface of thedialysis machine can take place pneumatically, for example. For thispurpose, usually an air cushion is provided which is filled withcompressed air and thus presses the cassette onto the coupling surface.

The cassette receiver usually has a receiver surface which is disposedopposite the coupling surface and into which the rigid base of thecassette is inserted. The receiver surface advantageously hascorresponding recesses for this purpose. The receiver surface with theinserted cassette can then be pressed onto the coupling surface via apneumatic pressing apparatus.

The insertion of the cassette can take place in different ways. In thedialysis machine which is shown in FIG. 6, a drawer 11 can be moved outof the dialysis machine to receive the cassette. The cassette isinserted into this drawer. The cassette is then pushed into the dialysismachine together with the drawer. The pressing of the cassette with thecoupling surface which is arranged in the interior of the apparatus iscarried out by moving the cassette and the coupling surface mechanicallytoward one another and then pressing them together pneumatically.

The coupling of a cassette 110 with the dialysis machine of FIG. 8 willnow be described with reference to FIG. 10. The coupling surface 130 isfreely accessible by opening a door 140 so that the cassette can bearranged at the correct position at the coupling surface 130. Thecoupling surface 130 is in this respect inclined rearwardly toward thevertical, which enables an easier coupling. The door 140 can then beclosed so that a receiver surface at the door comes into contact withthe rear side of the cassette. The pressing takes place by an aircushion arranged in the door. In addition, a vacuum is applied betweenthe coupling surface and the cassette 110.

The dialysis machine of FIG. 6 also has an apparatus for automaticconnecting. A connector receiver 112 is provided for this purpose intowhich the connectors of the dialysate bag 10 are inserted. The connectorreceiver 112 then moves into the apparatus where a barcode reader isprovided which reads the barcodes applied to the connectors. Theapparatus can thus check whether the correct bags were inserted. If thecorrect bags are recognized, the connector receiver 112 moves incompletely and so connects the connectors of the bag to the connections11 of the cassette made as connectors.

In the dialysis system of FIG. 10, hose sections are arranged at theconnections 11 of the cassette and for manual connection to thecorresponding bags via connectors.

2.3 Pump Actuators

The pumping of the liquid through the fluid system takes place by amembrane pump which is formed by the pump chambers 53 and 53′ togetherwith the flexible film of the cassette. If the flexible film is pressedinto the pump chamber by a corresponding pump actuator, fluid is pumpedout of the pump chamber into the opened regions of the fluid paths ofthe cassette. Conversely, fluid is sucked out of the fluid paths andinto the pump chamber by pulling the film out of the pump chamber.

The pump stroke in this respect takes place by movement of a pumpactuator into the pump chamber. The pump actuator is moved away from thepump chamber again for the suction stroke. An underpressure arises inthis respect due to the airtight pressing of cassette and couplingsurface by which the flexible film of the cassette follows the pumpactuator and is thus pulled out of the pump chamber again.

To enable a good coupling of the pump actuator to the flexible film ofthe cassette, a vacuum system can be provided. In this respect, theforce with which the flexible film is moved away from the pump chamberat a maximum during a suction stroke can be set via the setting of acorresponding vacuum between the coupling surface and the cassette. Thesuction force of the pump can hereby be set very finely. The pump forceis in contrast set by the thrust force of the actuator.

The balancing of the fluid flows can in this respect take place by thecounting of the suction and pump strokes since the membrane pump has ahigh precision of the fluid quantity pumped with each stroke.

2.3.1. Hydraulic Drive

The structure of a first embodiment of a pump actuator is shown in FIG.11. The pump actuator is moved hydraulically in this respect. A membrane59 is provided for this purpose which is placed at the flexible film ofthe cassette. The membrane 59 can be produced, for example, fromsilicone. A chamber 54 which can be filled with hydraulic fluid isprovided behind the membrane 59. By application of an overpressure inthe chamber 54, the membrane 59, and with it the flexible film of thecassette, is pressed into the pump chamber 53 of the cassette. Byapplication of an underpressure to the chamber 54, the membrane 59 is,in contrast, pulled into the chamber 54. Due to the underpressurebetween the flexible film of the chamber and the membrane, the flexiblefilm follows this movement so that the volume of the pump chamber 53increases. The pump process with the pump stroke and the suction strokeis shown schematically in FIG. 12 b.

A hydraulic pump 58 is provided for the operation of the pump hydraulic.It has a cylinder in which a piston can be moved to and fro via a motor57. The hydraulic fluid is hereby pressed into the chamber 54 or suckedout of it again via a corresponding connection line. A position encoder56 is provided at the hydraulic pump 58 in this respect and the movementof the piston can be recorded via it. It can hereby be determined howmuch hydraulic fluid was pressed into the chamber 54 and how muchhydraulic fluid was removed from it. Pressure sensors 55 are alsoprovided at the hydraulic system which measure the pressure in thehydraulic system. They on the one hand allow a functional check of thehydraulic system since the data of the pressure sensors can be comparedwith those of the position encoder 56 and the leak tightness of thehydraulic system can hereby be checked.

In addition, the pressure sensors allow a determination of the pressurein the pump chamber 53 of the cassette. If the hydraulic pump 58 is notmoved, a pressure balance is adopted between the chamber 54 and the pumpchamber 53. The pressure of the hydraulic fluid thus corresponds to thepressure in the pump chamber 53.

The coupling procedure of the pump actuator to the pump chamber 53 isshown in FIG. 12a . In this respect, the chamber 54 is first loaded withhydraulic fluid such that the membrane 59 arches outwardly for thepreparation of the coupling. The coupling surface and the cassette arethereupon moved toward one another so that the membrane 59 presses theflexible film of the cassette into the pump chamber 53. After thepressing of the coupling surface and of the cassette, the space betweenthe membrane and the flexible film is outwardly closed in an airtightmanner so that the flexible film follows the movement of the membrane.This is shown in FIG. 12 b.

The pump actuator shown in FIG. 11 is in this respect implemented in thedialysis machine of FIGS. 6 and 7. In this respect, a corresponding pumpactuator is respectively provided for each of the two pump chambers 53and 53′.

2.3.2 Electromechanical Drive

Alternatively, the pump actuator can be operated in an electric motormanner. A correspondingly shaped ram is provided for this purpose whichis pressed toward or away from the flexible film via an electricmotor(e.g., via a stepped motor), and the pump stroke or suction strokeis thus generated. Such pump actuators 151 and 152 are shown in thedialysis system of FIG. 10. A vacuum system is also provided whichensures that the flexible film also follows the ram in the suctionmovement.

2.4 Valve Actuators

A valve plunger can be provided as the valve actuator which presses theflexible film of the cassette into a corresponding chamber of the rigidbase and closes the fluid passage in this region. The valve actuatorcan, for example, be pneumatically actuated. The plunger can in thisrespect be biased via a spring so that it either opens without pressureor closes without pressure.

Alternatively, the valve actuator can be implemented via a flexiblemembrane which is moved hydraulically or pneumatically. The flexiblemembrane is in this respect moved toward the cassette by application ofpressure and so presses a corresponding valve region of the flexiblefilm into a fluid passage to close it.

Valve actuators 71, which are coupled to the valve regions V1 to V16 ofthe cassette, can be recognized on the coupling surface in FIG. 10.

2.5 Sensors

The dialysis machine has sensors via which the machine can be controlledor its proper functioning can be monitored.

One or more temperature sensors are provided via which the temperatureof the dialysate and/or of the heating elements can be measured. In thedialysis machine of FIGS. 6 and 7, the temperature sensors are arrangedat the coupling surface to the cassette and can thus measure thetemperature of the dialysate flowing through the cassette. In thedialysis machine of FIGS. 8-10, in contrast, a temperature sensor 88 isprovided on the heating plate 68 which measures the temperature of thedialysate present in the bag 67. Temperature sensors can furthermore beprovided at the heating element or elements.

One or more pressure sensors can also be provided to determine thepressure in the pump chambers. Such sensors can help to ensure thatdialysate is not pumped to the patient at too high a pressure and/orthat the suction pressure does not become too high upon pullingdialysate from the patient.

In the dialysis machine of FIGS. 6 and 7, the pressure measurement takesplace via pressure sensors in the hydraulic system of the pumpactuators, as was shown above. In the dialysis machine of FIGS. 8-10, incontrast, pressure sensors 85′ and 86′ are provided in the couplingsurface which directly measure the pressure in corresponding pressuremeasurement regions of the cassette. The coupling of these pressuresensors to the cassette is in this respect advantageously ensured by avacuum system.

2.6 Input/Output Unit

The dialysis machine also includes an input/output unit forcommunication with an operator. A corresponding display is in thisrespect provided for the output of information which can, for example,be implemented by light-emitting diodes, LCD displays or a screen.Corresponding input elements are provided for the inputting of commands.Push buttons and switches can, for example, be provided in this respect.

In each of the above described dialysis machines of FIGS. 6-10, a touchscreen 120 is provided which allows an interactive menu navigation.Display elements 121 and 122 are also provided which show states of thedialysis machine in compact form.

The dialysis machine of FIGS. 6 and 7 also has a card reader 125 viawhich a patient card can be read. Data on the treatment of therespective patient can be stored on the patient card. The treatmentprocedure for the respective patient can hereby be individually fixed.

The peritoneal dialysis machine also has an acoustic signal unit viawhich acoustic signals can be output. In this respect, an acousticwarning signal can in particular be output when an error state isregistered. A loudspeaker is in this respect advantageously provided viawhich the acoustic signals can be generated.

2.7 Controller

The peritoneal dialysis also has a controller by which all componentscan be controlled and monitored. The controller provides the automaticprocedure of the treatment.

The basic structure of an embodiment of such a controller is shown inFIG. 13.

The communication with the operator and with external informationsources in this respect takes place via an interface computer 150. Itcommunicates with a patient card reader 200, an input and output unit(e.g., touchscreen) 210 which serves communication with the patient andwith a modem 220. Updated software can, for example, be uploaded via themodem 220.

The interface computer 150 is connected via an internal bus to anactivity computer 160 and to a safety computer 170. The activitycomputer 160 and the safety computer 170 generate redundancy of thesystem. The activity computer 160 in this respect receives signals fromthe sensors of the system and calculates the control signals for theactuators 180. The safety computer 170 likewise receives signals fromthe sensors 180 and checks whether the commands output by the activitycomputer 160 are correct. If the safety computer 170 determines anerror, it initiates a corresponding emergency procedure. The safetycomputer 170 can in particular trigger an alarm signal in this respect.The safety computer 170 can furthermore close the access to the patient.A special valve is arranged at the output of the cassette at the patientside for this purpose and only the safety computer 170 has access to it.This safety valve is in this respect closed in the pressureless state sothat it closes automatically on a failure of the pneumatic system.

The safety computer 170 is also connected to the barcode reader 190 andso checks the connection of the correct dialysis bags.

A diagnosis system 230 is furthermore provided via which errors of thesystem can be determined and remedied.

3. Heating Systems and Methods

Heating systems and methods that can be used in one of the dialysissystems presented above or in one of the dialysis machines presentedabove will now be described. The heating systems and methods describedcan, for example, be used for the control of a heater as was describedin Section 2.1.

FIG. 14 shows an embodiment of a heating control unit 310 by which twoheating elements HT1 and HT2 of a heater are controlled. The heatingcontrol unit includes a first switching element 311 by which the firstheating element HT1 can be switched on and off and a second switchingelement 312 by which the second heating element HT2 can be switched onand off. In this respect, mains voltage applied at the supply lines 301and 302 is applied at or removed from the two heating elements by theswitching elements 311 and 312. The two switching elements 311 and 312are in this respect controlled by the heating control unit 310 and thusform a switching arrangement. The switching elements 311 and 312 can,for example, be triacs. The mains voltage can in this respect be appliedto the two lines 301 and 302 without a galvanic isolation.Alternatively, the mains voltage can be applied to the lines 301 and 302via a galvanic isolation, for example via an isolating transformer.

The heating control unit 310 also has measuring connections 313 and 314for connection to the mains voltage. In this respect, a monitoringarrangement is provided which recognizes the zero crossings of the mainsvoltage. The switching arrangement can in each case be actuated in thezero crossing of the mains voltage to switch the heating elements on oroff. In this respect, the power of the heating is controlled via theswitching on and off of one or more half cycles of the mains voltage,for example via the ratio of the half cycles with switched on heatingelements to the number of the half cycles with switched off heatingelements.

The two heating elements HT1 and HT2 can be switched on and offindependently of one another by the switching arrangement. Inalternative embodiments, only one heating element HT1 or HT2 isprovided.

A control can thus be realized by the corresponding setting of thenumber of the half cycles with a switched on heating element or switchedon heating elements which makes it possible to realize between 0 and100% of the heating power. A temperature regulation can be provided inthis respect in which the ratio of the number of the half cycles with aswitched on heating element to the number of the half cycles with aswitched off heating element is set on the basis of a temperature sensorreading.

The heater can be operated at different rated voltages of the mainspower supply. The monitoring arrangement of the heating control unit 310measures the level of the mains voltage and accordingly adapts thecontrol of the heating element or elements to the found level of themains supply. A desired power can hereby also be set precisely withdifferent and/or fluctuating mains voltages and the same maximum powerof the heating can be achieved at different mains voltages. Such anadaptation to different mains voltages is advantageously combined with atemperature regulation in this respect.

The use of two heating elements HT1 and HT2 controllable independentlyof one another in this respect enables a particularly favorableadaptation to different mains voltages. The two heating elements can inthis respect be operated simultaneously in a first operating mode. Bothheating elements can, for example, have mains voltage half cyclesapplied synchronously in this respect. In this operating mode, the twoheating elements therefore work essentially as two heating elementsconnected in parallel and having only one control. Such an operatingmode can be used with a low mains voltage of, for example, 100 V or 120V in order also to provide sufficient maximum heating power at such alow mains voltage. The control in this respect advantageously switchesinto the first operating mode when it recognizes a mains AC voltage in afirst voltage range which advantageously includes voltages of 100 V and120 V. In some embodiments, the first voltage range extends from 80 V to160 V. In order to set the heating power to a desired value, the twoheating elements can be switched off both synchronously and alternatelyto set the corresponding ratio of the number of the half cycles with aswitched on heating element to the number of the half cycles with aswitched off heating element to the desired value.

If it is a case of two heating elements of identical rated power, thenumber of the half cycles with a switched on first heating element HT1and the number of the half cycles with a switched on second heatingelement HT2 can be added for calculating this ratio. The number of thehalf cycles with switched off heating elements can equally be added. Ifthe two heating elements in contrast have different rated powers, thishas to be taken into account by a corresponding factor.

In the second operating mode, the two heating elements HT1 and HT2 incontrast each alternately have mains voltage half cycles applied. Thissecond operating mode is used with a rated voltage of 230 V or 240 V.The control in this respect advantageously switches into the secondoperating mode when it recognizes a mains AC voltage in a second voltagerange which includes higher voltages than the first voltage range. Thesecond voltage range can include voltages of 230 V and 240 V. In someembodiments, the first voltage range extends from a voltage larger than160 V onward. Since mains voltage is applied in each case at a maximumto one of the two heating elements in the second operating mode, themaximum current power consumption can be kept below the permittedamperage of, for example, 16 A. To set the maximum heating power in thisrespect to a desired value, for example to the maximum heating power inthe first operating mode, the two heating elements can also both beswitched off to set the corresponding ratio of the number of the halfcycles with a switched on heating element to the number of the halfcycles with a switched off heating element to a desired value.

Embodiments for a second operation mode and for a first operating modeare shown in FIGS. 15a and 15b . In the second operating mode,respective individual half cycles are switched alternately to the firstheating element HT1 and to the second heating element HT2 in FIG. 15a .As shown in FIG. 15a , in this respect the upper half cycles 321 areswitched to the first heating element HT1, and the lower half cycles 322are switched to the second heating element HT2. The switch over could,however, take place in each case after a larger number of half cycles.In a subsequent time section, only the lower half cycles 323 areswitched to the second heating element HT2, whereas the upper halfcycles remain completely switched off. In this respect, individual halfcycles could also be switched off so that there are breaks in each casebetween the alternating action on the first heating element and on thesecond heating element in which half cycles remain completely switchedoff.

In the first operating mode illustrated in FIG. 15b , in contrast, boththe upper half cycles 324 and the lower half cycles 325 are switched toboth heating elements HT1 and HT2. A correspondingly higher power canhereby be provided.

In some embodiments, the control makes the determination whether acontrol of the heating elements HT1 and HT2 takes place synchronously(e.g. in each case in parallel with full cycles) or alternately (e.g. ineach case with half cycles) in dependence on the detected mains ACvoltage. The heating is in this respect configured so that the fullheating power can be provided in synchronous operation at a minimumoperating voltage (e.g., 80 V) and a duty cycle of 100%. From apredetermined limit voltage (e.g., 160 V) onward, the heating elementsare in contrast each operated alternately, with the heating elementsalternately controlled separately with a half cycle (positively ornegatively).

An adaptation of the power to the operating voltage above the minimumoperating voltage takes place by a corresponding reduction of thetransmitted full cycles or half cycles, with the heating power beingreduced by 50% with respect to synchronous operation in the secondoperating mode.

The heating elements can in particular be ohmic heating elements. Theycan, for example, have a resistance between 10 and 50 ohms. The desiredmaximum heating power in this respect in particular amounts to between200 W and 2000 W, for example, in particular to approximately 800 W.

Two alternative embodiments will now be specifically described. Themaximum desired heating power should in this respect amount to 800 W ineach case.

In a first embodiment, two heating elements having a resistance of 16ohms are used. They can provide the desired heating power of 800 W witha rated voltage of 110 V, also when taking account of an undervoltage of80 V in the first operating mode, with a current of 10 A resulting. Inthis respect, both heating elements are controlled in parallel with thefull sine wave. If the voltage is actually 110 V, a heating power of1512 W would result with a full control of both heating elements. Inaccordance with the measured voltage, individual half cycles areaccordingly therefore switched off either at one heating element or atboth of the heating elements to set the maximum heating power to thedesired 800 W. At a voltage of 100 V, around 52% of all voltage halfcycles are therefore actually switched on and the others are switchedoff.

At a voltage of 240 V, work is carried out in the second operating modein which always, at a maximum, one of the two heating elements isswitched on. At a resistance of the heating elements of 16 ohms in eachcase, a maximum current flow of 15 A results in this respect.

In an operation in which each half cycle is switched either to the oneheating element or to the heating element a heating power would in thisprocess result of 3600 W. In dependence on the mains voltage, acorresponding number of half cycles is therefore completely suppressedto set the heating power to the desired maximum value of 800 W. At anactual rated voltage of 240 V, only 22% of all the half cycles aretherefore switched either to the one or to the other heating element sothat the averaged amperage falls accordingly. Only 11% of the heatingpower or of the half cycles available in the equiphase full cycleoperation is thus used.

In the second specific embodiment, two heating elements, each having 25ohms, are used. At an effective mains voltage of 100 V, such as ispresent in Japan, each of the two heating elements thus has a maximumheating power of 400 W. In the first operating mode, in which bothheating elements are controlled in an equiphase manner in full cycleoperation, exactly the desired heating power of 800 W thus results.

At an effective mains voltage of 120 V, such as is found in the UnitedStates, a maximum power of 576 W in contrast results for each of the twoheating elements in equiphase fully cycle operation. To reduce the totalpower down to 800 W, the number of the half cycles of the mains voltageused for heating the heating elements is therefore reduced accordinglyby a complete switching off of individual half cycles. In this respect,work can continue in equiphase and individual ones of the half cyclescan be completely switched off or individual half cycles can only beswitched off for one of the two heating elements. The reduction in thepower to the desired 400 W in this respect results from the use of only69% of all half cycles.

Only 177 pulses are therefore used for heating in relation to 255pulses. At a rated voltage of 240 V, the heating is, in contrast,operated in the second operating mode in which the first and the secondheating elements are each operated alternately. If each half cycle wereused here for operating one of the two heating elements, this wouldresult in a heating power of approximately 2300 W. To reduce the heatingpower to the desired 800 W, a corresponding portion of half cyclestherefore has to be completely suppressed so that only around 35% of allhalf cycles are used at one of the two heating elements and thus onlyaround 17% of the heating power or half cycles available in equiphasefull cycle operation is used.

The half cycles or packets of half cycles are in this respectadvantageously switched so that no temperature fluctuation occurs at theheating element, that is, the switching should take place faster thanthe sluggishness of the heating elements.

For example, the control can take place in this respect so that theratio of the half cycles with a switched on heating element and with aswitched off heating element is in each case kept to a desired valueaveraged over a specific number of pulses or a specific time. The ratiocan, for example, in this respect be set over a period of, for example,255 half cycles.

In this respect, the present invention is, however, not restricted toswitching individual half cycles. Pulse packets having a plurality ofhalf cycles can rather likewise be switched.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Otherembodiments are within the scope of the following claims.

What is claimed is:
 1. A dialysis machine comprising: a pump for pumpinga medical liquid; a heater for heating the medical liquid, the heaterhaving at least one heating element and a heating control unit, which isconfigured to be connected to mains AC voltage, connected to the heater,the heating control unit comprising a monitoring arrangement configuredto recognize zero crossings of the mains AC voltage and to detect alevel of the mains AC voltage and a switching arrangement configured toswitch the at least one heating element on or off in the zero crossing,wherein the heating control unit is configured to control power of theheater by switching on and off one or more half cycles of the mains ACvoltage, a temperature sensor, wherein the heating control unit isconfigured to set a ratio of a number of half cycles with a switched onheating element to a number of half cycles with a switched off heatingelement based on a signal of the temperature sensor and the detectedlevel of the mains AC voltage.
 2. The dialysis machine of claim 1,wherein the heater comprises two heating elements, wherein the twoheating elements are operated partly or fully synchronously.
 3. Thedialysis machine of claim 1, wherein the heating control unit generatesand superimposes a control signal based on a signal of the temperaturesensor on a control signal for adapting the power to the detected levelof the mains AC voltage.
 4. The dialysis machine of claim 1, wherein theratio of the number of half cycles with a switched on heating element tothe number of half cycles with a switched off heating element is setsmoothly in time and directly in dependence on the signal of thetemperature sensor and of the detected level of the mains power supply.5. The dialysis machine of claim 1, wherein the temperature sensordetermines the temperature of the medical liquid to be heated.
 6. Thedialysis machine of claim 1, wherein the dialysis machine is aperitoneal dialysis machine and the heater is configured to heatdialysate.
 7. The dialysis machine of claim 6, wherein the temperaturesensor determines the temperature of the dialysate.
 8. The dialysismachine of claim 1, further comprising a cassette for controlling theflow of the medical liquid, the cassette being coupled to a couplingsurface of the dialysis machine and comprising at least one pumpingchamber of the pump.
 9. The dialysis machine of claim 8, wherein thecassette comprises a heating region that is in contact with the heatingelement of the dialysis machine.
 10. The dialysis machine of claim 9,wherein the temperature sensor is provided in the coupling surface ofthe dialysis machine and contacts a temperature sensor region of thecassette located at the inflow or at the outflow of the heating regionin order to measure the temperature of the medical liquid flowing in orout of the heating region of the cassette.
 11. The dialysis machine ofclaim 8, further comprising a heating bag connected to the cassette, theheating element being arranged in a heating plate that contacts theheating bag.
 12. The dialysis machine of claim 11, wherein thetemperature sensor is arranged in the heating plate to contact theheating bag in order to measure the temperature of the medical liquid inthe bag.
 13. A method of operating a dialysis machine comprising a pumpfor pumping a medical liquid and a heater for heating the medicalliquid, the method comprising: detecting zero crossings and a level of amains AC voltage; and switching at least one heating element of theheater on or off in the zero crossing, wherein a power of the heater iscontrolled based on a number of the half cycles of the mains AC voltagewith a switched on heating element, wherein a level of the mains ACvoltage is detected, and wherein a ratio of the number of the halfcycles with a switched on heating element to a number of a half cycleswith a switched off heating element is set based on a signal of thedetected level of the mains AC voltage.
 14. A dialysis machinecomprising: a pump for pumping a medical liquid; a heater for heatingthe medical liquid, the heater having at least one heating element and aheating control unit, which is configured to be connected to mains ACvoltage, connected to the heater, the heating control unit comprising amonitoring arrangement configured to recognize zero crossings of themains AC voltage and to detect a level of the mains AC voltage and aswitching arrangement configured to switch the at least one heatingelement on or off in the zero crossing, wherein the heating control unitis configured to control power of the heater by switching on and off oneor more half cycles of the mains AC voltage, wherein the heating controlunit is configured to set a ratio of a number of half cycles with aswitched on heating element to a number of half cycles with a switchedoff heating element based on the detected level of the mains AC voltage.15. The dialysis machine of claim 14, wherein the monitoring arrangementand the heating control unit are configured to adapt power of the heaterto fluctuating voltage levels of the mains power supply, so that thesame maximum power of the heating is available independently of thelevel of the mains power supply.
 16. The dialysis machine of claim 14,wherein the heater comprises two heating elements that can be operatedin a first and a second operating mode, wherein the heating controlselects the first operating mode on detection of a mains AC voltagewhich is in a first, lower voltage range and the second operating modeon detection of a mains AC voltage in a second, higher voltage range.17. The dialysis machine of claim 16, wherein, while operating in thefirst or second operating mode, the heater control sets the ratio of thenumber of the half cycles with a switched on heating element to thenumber of the half cycles with a switched off heating element independence on the level of the detected mains AC voltage within therespective voltage range in which an operation takes place in the firstor second operating mode, thereby keeping the maximum power of theheating constant or setting a desired power irrespective of voltagefluctuations within the respective voltage range.
 18. The dialysismachine of claim 14, wherein the ratio of the number of half cycles withswitched on heating element to the number of half cycles with switchedoff heating element is set smoothly in time and directly in dependenceon the detected level of the mains power supply.
 19. The dialysismachine of claim 14, further comprising a temperature sensor, whereinthe heating control unit is configured to set a ratio of a number ofhalf cycles with switched on heating element to a number of half cycleswith switched off heating element based on a signal of the temperaturesensor and the detected level of the mains AC voltage.
 20. The dialysismachine of claim 19, wherein the heating control unit generates acontrol signal based on a signal of the temperature sensor which issuperimposed on control signals for adapting the power to the detectedlevel of the mains AC voltage.
 21. The dialysis machine of claim 19,wherein the temperature sensor determines the temperature of the medicalliquid to be heated.
 22. The dialysis machine of claim 19, wherein thedialysis machine is a peritoneal dialysis machine and the heater isconfigured to heat dialysate.
 23. The dialysis machine of claim 22,further comprising a cassette for controlling the flow of the medicalliquid, the cassette being coupled to a coupling surface of the dialysismachine and comprising at least one pumping chamber of the pump, whereinthe cassette comprises a heating region that is in contact with theheating element of the dialysis machine.
 24. The dialysis machine ofclaim 23, comprising a temperature sensor provided in the couplingsurface of the dialysis machine and contacting a temperature sensorregion of the cassette located at the inflow or at the outflow of theheating region in order to measure the temperature of the medical liquidflowing in or out of the heating region of the cassette.
 25. Thedialysis machine of claim 22, further comprising a heating bag connectedto the cassette, the heating element being arranged in a heating platethat contacts the heating bag, wherein a temperature sensor is arrangedin the heating plate to contact the heating bag in order to measure thetemperature of the medical liquid in the bag.